In recent years, the wave of digitization is rapidly coming into the field of image recording. Particularly, the textile printing industry is paying more attention to inkjet type image recording apparatuses suitable for quick response and high-mix low-volume textile printing than to known screen textile printing methods. Likewise, also, the hope of the sign display industry is placed on inkjet type image recording apparatuses that can form images more simply at a lower cost than known screen printing or graver printing.
In the textile printing industry, cloths with low rigidity are main recording media, and in the sign display industry, a woven plastic material (vinyl chloride) is utilized as well as paper or the like. In a case where such a material with low rigidity is employed as a recording medium, the recording medium is usually conveyed by an endless belt to an image recording section including recording heads and others. In such an image recording apparatus, image recording by jetting ink from the recording heads has such a problem that the ink having been jetted from the recording heads may adhere to the conveying belt and the deposited ink stains the recording medium. Therefore, it is necessary to clean the conveying belt.
As an image recording apparatus that performs cleaning of a conveying belt, there is known an image recording apparatus having a cleaning roller formed by a sponge and arranged to be rotatable and contactable with a conveying belt in a state where a lower part of the cleaning roller is dipped in a cleaning liquid in a cleaning liquid bath. The conveying belt is moved in contact with the cleaning roller, and thus the cleaning roller removes dirt of ink deposited on the conveying belt and the like (for example, see Patent Document 1).
In such an image recording apparatus, ink removed from a conveying belt by a cleaning roller gets dissolved into cleaning liquid in a cleaning liquid bath, and ink density of the cleaning liquid in the cleaning bath gradually increases. When the ink density in the liquid bath becomes high, not only the cleaning effect gets lost, but also the conveying belt is contaminated rather more, resulting in staining a recording medium. Therefore, the cleaning liquid is replaced by new cleaning liquid, as necessary. In a known image recording apparatus, usually, when accumulated total moving length of a conveying belt in contact with a cleaning roller, or accumulated total time during which the conveying belt moves in contact with the cleaning roller, comes to a predetermined value, cleaning liquid is automatically replaced.
[Patent Document 1] TOKKAI No. 2003-205658
However, in the case of such a known image recording apparatus, cleaning liquid is equally replaced every time cleaning has been performed with cleaning liquid for a predetermined length or time. Therefore, in order to clean off dirt on a cleaning roller well in any case, the cleaning liquid must be frequently replaced, causing a problem of disposing cleaning liquid as liquid waste more than necessary.